Rheostat



Patented Nov. 2, 1926.

UNITED STATES PATENT OFFICE.

nnnos'rm.

Application filed October 20, 1922. Serial No. 595,732. r

This invention relates to improvements in rheostats for regulating oradjusting an electrical circuit and refers more particularly to animprovement in a contact member which is adapted for wiping engagementwith the coils of the rheostat-winding, and preferably of that type inwhich the winding is part cylindric and of oblong cross section and inwhich the contact-member wipes over the inner face of such winding. j

The present improvements are shown'in connection with a Vernier rheostatsuch as shown in my prior application for United States Letters Patent N0. 562,607, filed May 28th, 1922, but may be applied to single windingor one-stage rheostats. 5

The present invention relates more specifically to, and is animprovement on, the contact member of the main arm of the rheostatelement which is so constructed and arranged, in accordance with thepresent invention, as to provide'a wide area of contact between it andthe coils of the rheostat winding; which has large current carryingcapacity to avoid overheating of thecontact member; which can be made atless cost and is easy to assemble, and which contact mem-' ber is soconstructed and arranged that within itself and in its co-operation withits arm,

as to be resilient to efiect a good brush contact between it and thecoils of the rheostat,

and to provide for irregular surfaces on the winding.

In the drawings: Figure 1 is a plan of a rheostat embodying myinvention.

Figure 2 is an enlarged plan view of the main rheostat arm and itscontact member showing the latter partially in section.

Figure 3 is an edge view of said arm with the contact member shown insection;

Figure 4 is a perspective view of said contact member. L As shown in thedrawings, 10-de'signates a: winding which constitutes the principal partof a Vernier rheostat circuit, 11 a relatively short or fractional partof said circuit, 12 the main conducting arm of the rheostat whosecontact member travels against the inner sides otthe coils of winding10, and 13 designates the auxiliary or fractional conductor arm which iselectrically connected to the arm 12 and travels along the fractionalrheostat element or con-' 65 ductor 11.

The winding 10 is wound about and supported by an upstanding rim 14which is fixed on thebase 15 of the rheostat by the overlapping of theends of the open rimwith a lug 16 fixed to the base. 17, 18 designatebinding posts by which the rheostat circuit is connected to the wires ofan external circuit.

Referrin bination 0% elements which constitute the present invention,the same are made as folows:

The arm 12, which may be made of sheet metal, is provided at one endwith an opening 19, through which extends one of the operating shafts(not shown), and is provided at its other end with a reduced extension20. Said extension is shown. as extendingcentrallyfrom the end of thearm 12 and forms at the-base of the arm 20 transverse shoulders 21. Thetongue or extension 20 is widened at its base to produce a rivet member20' for a described.

22 designates a contact member which is fitted on the arm 12 and isadapted for brush contact with the coils of the winding 10. Said contactmember is made of a single piece of resilient sheet metal whichpossesses a good co-efiicient of current conductivity. The said contactmember can be madefrom a metal strip of equal width throughout itslength, and is provided at its end with slots, 23, 24-through which thearm extension 20 is adapted to extend. It.

is necessary that the contact-member be connected to said arm extensionin a-manner to'hold it firmly thereon, and forthis purpose the slot 23is made; to fit flat against the shoulder 21 and over" the rivet member20 which latter is swaged' at20 over the outer face of the contactmember around the opening 23 therein. Preferably the said slot and saidrivet member are oblong.

. The strip constituting said contact member is' bent to produce a loopformation -Wherein the terminals 25, 26 thereof are closed in overlappng but spaced relation upon each other. The intermediate portion of saidstrip is curved'to produce a wiping or brush face 28, which engages-thesides of the coils of the main winding 10 0f the now to the elements andcom- 7 on i rheostat circuit, the curvature of said intermediate portionof the strip being such as to provide a brush wiping contact thereofpressure due tothe 'the tongue or extension ,with the inner sides ofsaid coils. The said contact member is made of substantial depth, whenused in connection with the form of winding illustrated in my aforesaidapplication, so that the engagement between the contact member and thecoils of said winding will be throughout the width of the wiping curvedportion 28 of the contact. This construction of the contact member givesnot only a good contact between it and the coils of the main rheostatwinding, but also affords a large current carrying capacity at the.point where the contact member engages the winding so as to therebyavoid overheating of the contact member and winding at their points ofcontact. It is within the spirit of the invention, as herein claimed,however, to employ the resilient contact member with other forms ofrheostat windings.

The said aperture or slot 24 is made longer than the width of the armextension 20 so that the free end or terminal 26 of the contact member.can move freely relatively to the said tongue or extension, and therebygive ample the resilient contact member to adapt itself to the innerface of the main winding. Furthermore the self contained resiliency ofthe outer looped portion 28 of the contact member permits said member toyield inwardly after the free end 24 is brought up against the terminal25, and until said brush portion is sprung inwardly into contact withthe end of the tongue the final limit of resilient movement of thecontact member. It will thus be seen that the flexibility of the contactmember is produced both by the resiliency of the metal of which it isformed and by the slight freedom of movement afforded by the elongatedslot 24, The limiting stop formed by the end of 20 prevents the curvedbrush portion of the loop contact member from being bent so far inwardlyas to cause it to tend to take an inward set, should undue force beapplied to the brush face of said member at a time when the arm 12 isremoved from the connection to the rheostat structure.

An advantage of the construction shown is that the contact member 22described, and its co-operation with the arm 12, afiords a wide facebearing between said contact member andthe coils of the winding, and acontact which will be'firm by reason of the inherent resiliency of themetal forming the contact member and its anchorage connection to the befurthermore noted that a defective confreedom of adjustment to 20, whichconstitutes arm. It willtact member can be readily removedand a new oneplaced on the arm.

I claim:

1. A resilient contact member for the con- 7 ducting arm of a rheostatmadeof open looped formation to provide an intermediate curved brushsurface, the ends of said loop being folded back on each vided withregistering apertures.

2. A resilient contact member for the conducting arm of a rheostat madeof open looped formation to provide an intermediate curved brushsurface, the terminals of said loop being folded back on each other inoverlapped, spaced relation and said terminals being provided withapertures to engage over a support to which one of the terminals isattached. i"

3. A resilient contact member for the conducting arm of a rheostat madeof open looped formation to rovide an intermediate curved brush sur ace,the terminals of said loop being folded back on each other inoverlapped, spaced relation and said terminals being provided withapertures to enover a support to which one of the tergage minals isattached, the aperture of the other other and proterminal fittingloosely over said support.

T4. A contact device comprising an arm, and a looped resilient contactpiece, extending across an end of said arm and confined to the arm atboth ends limited movements between said arm and at least one end ofsaid contact piece.

5. A contact device comprising an arm and a looped resilient contactpiece extending across the end of said arm, one of the ends of saidcontact piece being fixedto the arm and the other end being secured tothe arm to permit limited relative movements between the same and thearm.

6. A contact device comprising an arm provided with a reduced extensionat one end forming an outwardly facing shoulder, and a resilient loopedcontact member having a curved intermediate contact face and provided atits ends with slots engaged over said extension.

7. A contact device comprising an arm provided with a reduced extensionat-one end forming on the arm an outwardly facing shoulder, a resilientlooped contact member having slots in its ends through which saidextension asses, said extension fitting into one of sai slots and beingloose in the other slot.

In witness as my invention, nature this 12 day CHESTER to permitrelative

